Inert monatomic gas shielded metalarc welding process



Dec. 5,1950. H. E. KENNEDY 2,532,410

INERT MONATOMIC GAS SHIELDED METAL-ARC WELDING PROCESS Filed Oct. 29, 1949 3-PHASE 1g A.C.

INVENTOR HARRY E.KENNE DY Patented Dec. 5, 1950 INERT MONATOMIC GAS SHIELDED "METAL' .ARC WELDING- PROCES S 'Harryf E'Kennedy, Berkeley, Calif., assignor to :T-herLinde Air ProductsuCompany, rte-corporationof .0hio

ApplicationOctoberQB, 1949,'-Serial No.' 1245.399

This invention relates to electric" welding,- and more particularly-to the metal-arc welding of-refractory oxide metals such as aluminum, stainless steeland'magnesium in a stream of inert mon- :3 Claims. (Cl. 219-. -1'0) cuit) and'l-fullload current values. rtial is relatively low andsafe-at all times.

the welding current; at a potential which isisubstantially constant between: no load (open cir- Such poten- The atomic gas such asargon and/or helium with-an resulting circuit.-is-simple,efficient, and easy to electrode of 'fi'ller'metal which is mechanically -maintain.

fed toward the welding zone. In. the drawing,'-.the single figure is a diagram- "In this'type ofwelding' it has been customary -matic view, .partly in elevation, of an inert in the past to control the'rod feed'speed by means -monat0mic-gas shielded metal-arc welding syswhich is responsiv'etochanges in the arc-voltage stem. illustrating the invention. so as to keep the arc voltage as constant as pos- As shown ntthe drawing-a bare rod ID of sible, the welding current sourcezhaving a droopaluminum, for example; is drawn fromra reel l2 ing voltage-current characteristic to stabilize the I-by'a wheel l lwhich-isdrivenby an electric motor operation and to provide a starting or open-cir- 1-6aat'arsubstantially:constant;speed determined Quit, Voltage which i b t ntially higher'than 1 m bythesetting-of-a rheostat I8 in the input cirthe welding-or arc voltage. Such controls are lcuit ofthe motor. :The rodis fedby the wheel expensive to buy and maintain, '14 through a welding gul'i- 22 containing a brush ,1 have discovered, however, that the inert.at- 2d, inelectricalecontact with the rod. An inert mosphere of argon and/or helium -;provides lmonatomic eso argon, for example, issupenough stabilizing influence on the arcin this Iii) p1 e 0 t -91 flo s e d e b h 2 type of welding to make possible the use of a and is discharged around the end portion of the current source of relatively low constant potend E! and against the Work W composed of tial, thereby eliminating the need for any stabialuminum Wh h is to be Welded. The brush 24 lizing reactance or resistance in the welding cird W W (co of Sheets held in ycuit, as well as th need f r an t m ti side contact) are connected directly to a constant trols; the rod being fed at any desired substanpotential Source Of Welding Current, S h as a tially constant rate toward the work. compound generator y leads 8 and 30 con- Therefore, according to the invention, there is sisting of insulated conductors of low resistance. provided a process of electric welding work 0011- e generator 26 s driven at a constant p e sisting of a refractory-oxide metal of the class gig; by an A. C. motor 32 which is connected to an consisting of aluminum, stainless steel, and magpp y line 34 through 3 Switch he nesium, which comprises a pl in a r l tiv l shunt field winding 38 of the generator is sepalow (20-28 volts) potential of a Welding current y excited m a upp y line throu h source across a welding rod of such metal and a rheostat 0, While the Series fi Winding 42 the work, discharging a, stream of inert men. )4, and the interpole winding 44 are connected in atomic gas of the class consisting :of argon and series with the output circuit 46. The generator helium around the end portion of such rod and 25 Should e an Output voltage of between 20 against the work, and rapidly feeding such rod d 30 volts d current p y of sev ral toward the work at a substantially constant hundred amper The generate! olta e-Curspeed As the end of the rod touches the work, rent characteristic ShOllld be flat to within $0.5 the welding current from such source flows Volts between o load (Open cui and full through the end of the rod and the work, fusing l d values. the metal under the stream of inert gas and In operation, the rod I0 is fed toward the work starting the operation. The rod is then moved W at full speed, after the inert gas has been with the so discharged gas stream along a deturned on and the welding gun has been pointed sired path to be welded on the work, while the toward the work and positioned close enough to potential of the welding current source is kept the starting point so that the inert gas stream at substantially the same relatively low voltage 48 flows over the work. When the end of the rod as at the start of the operation, and. the rodtouches the work, current flowing from the genfeeding movement is also kept at the same rapid {)0 erator through the rod and work, fuses the end rate as at the start of the operation. The welding of the rod and the adjacent work metal, starting current source may be a compound generator the weld. The gun is then moved along a desired having a relatively flat voltage-current characpath to be welded in the work, while the rod feed teristic, or a standard welding generator providis kept at substantially the same rapid rate. The ed with a voltage regulator adapted to supply generator also keeps the potential applied between the rod and the work at the same substantially constant voltage.

The stream of argon not only protects the heated metal from oxidation, but also stabilizes the arc to such an extent that automatic variations of the rod feed to keep constant the arc length are not necessary. Also, the new system avoids the need for any are stabilizing resistance or reactance in the welding circuit. The resulting welds are clean, free of flux, and sound.

While direct current is preferred for welding, according to the invention, alternating current may be used without departing therefrom.

Iclaim: a 1. An inert monatomic gas-shielded metal-arc welding process which comprises applying a relatively low voltage of the order of 20 to 28 volts from a welding current source of constant potential across a bare metal welding rod and metal work composed of a refractory-oxide metal selected from th class consisting of aluminum, stainless steel and magnesium, discharging a stream of inert monatomic gas around'the end portion of such rod and against the work, feeding the rod toward the work at a substantially constant relatively rapid rate suflicient for fusing the end of such rod and the adjacent work metal with Welding current flowing from such source through the end portion of the rod and the work under such stream of inert gas, and moving the rod and gas stream along a desired path to be welded on the work while maintaining substantially constant both the rapid rate of rod feed and the relatively low voltage of such potential.

2. An inert gas shielded metal-arc welding system comprising the combination of means including a motor for feeding a bare welding rod composed of a refractory-oxide metal selected from the group consisting of aluminum, stainless steel and magnesium at a substantially constant speed toward work composed of a like metal, a brush in contact with such rod, a constant potential source of welding current, leads of relatively low resistance connecting such source directly to said brush and the work, and means including a welding gun for conducting an inert monatomic gas over such brush and then discharging a stream of such gas around the end portion of such rod and against the work, which gas not only prevents oxidation of the heated metal but also stabilizes the arc to such an extent that the need for any resistance or reactance component in' the welding circuit is avoided.

3. Process of welding which comprises supporting in side-by-side relation sheets composed of a refractory-oxide metal selected from the group consisting of aluminum, stainles steel, magnesium, and the alloys thereof, moving a welding gun along a path parallel to the seam formed by such sheets, feeding a welding rod through such gun toward such seam at a relatively constant rate, discharging from such gun around the emerging end portion of such rod a stream of inert monatomic gas selected from the group consisting of argon and helium, supplying welding current to such sheets and rod from a substantially constant potential source, and progressively fusing the end of the rod and the sheets along such seam under such inert gas stream which stabilizes the operation.

HARRY E. KENNEDY.

REFERENCES CITED The following references are of record in the fileoi this patent:

UNITED STATES PATENTS Number 7 Name Date 1,669,099 Noble May 8, 1928 2,300,670 Hopkins Nov. 3, 1942 2,332,950 Tannheim Oct. 26, 1943 

